1. Field of the Invention
This invention relates to silicone-based weatherable abrasion resistant coating compositions, methods of preparation and use, and coated articles.
2. Description of the Prior Art
There have been many attempts by others to provide abrasion resistant coating compositions which possess optimum balance of properties. Especially in the field of coating thermoplastics, the achievement of this goal has been elusive. Clark, Belgian Pat. 821,403, shows a coating composition comprising a dispersion of colloidal silica in lower aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH).sub.3 in which R is selected from the group consisting of alkyl radicals of 1 to 3 inclusive carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the gamma-methacryloxypropyl radical, at least 70 weight percent of the silanol being CH.sub.3 Si(OH).sub.3, said composition containing 10 to 50 weight percent solids consisting essentially of 10 to 70 weight percent colloidal silica and 30 to 90 weight percent of the partial condensate, said composition containing sufficient acid to provide a pH in the range of 3.0 to 6.0. Clark's coating composition achieves the goal of adequate abrasion resistance, but it suffers from a few disadvantages; for example, it crazes after being soaked in water and it does not weather adequately.
Several patents assigned to Du Pont, U.S. Pat. Nos. 3,429,845; 3,429,846; 3,651,003; and 3,819,562 show abrasion resistant coatings based on fluorocarbon monomers and monomers containing hydroxyl groups and glycidyl groups. The latter coatings are difficult to apply, poor in humidity resistance, and expensive.